Screw thread gage



Sept. 11, 1956 wdw H 1 9 7U, a r/ .I/

SCREW THREAD GAGE N. H.,' assignor to Bryant H'esslar H. Gates, Charlestown, a v

Springfield, Vt.',. a corpo- Chucking Grinder Company, ration of Vermont This invention relates to screw thread gaging, and has for an object to so form the gaging anvils that when they are retracted from engagement with the threads. of the work piece they will present smooth portions loosely fitting the threaded work and acting as guides to facilitate the placing or withdrawal of the work with respect to the gage. Thus as applied to a gage for gaging internal threads, these smooth or unthreaded anvil portions will present when the gage is open a smooth guiding portion of slightly less diameter than the internal thread crests of the work piece, while as applied to a gage for external threads, the unthreaded anvil portions, when the gage is open, will present a guiding portion of slightly greater diameter than the external thread crests of the work piece.

For a more complete understanding of this invention, reference may be had to the accompanying drawings in which:

Figure 1 is a top plan view of an internal thread gage showing an internally threaded ring in gaging position thereon, the thread gaging anvils being constructed in accordance with this invention.

Figure 2 is a view of the upper portion of the gage, the major portion of which is a sectional view on line 2E-2 of Figure 1.

Figure 3 is a sectional view to a larger scale on line 3--3 of Figure 2, the gage being closed.

Figure 4 is a view similar to Figure 3, but showingthe gage in open condition.

Figure 5 is a detail sectional view on line 5-5 of Figure 3.

Figure 6 is a detail sectional view on line 6-6 of Figure 4.

Figure 7 is a view similar to Figure 1, but. showing an externally threaded gage and a work piece.

Figure 8v is a sectional view on line 8-8 of Figure 7.

Figure 9 is a sectional view to a larger. scale on line 9-9 of Figure 8, the gage being shown closed.

Figure 10 is a view similar to Figure 9, but showing the gage open.

Figure 11 is a detail sectional view on line 11-11 of Figure 9, and Figure 12 is a detail sectional view on line 1212 of Figure 10.

Figure 13 is a view similar to Figure 9 but showing a modification.

Figure 14 is a detail sectional view on line 14-14 of Figure 13.

Referring first to Figures 1 to 6, the invention is shown as embodied in an internal thread gage. As shown in Figures 1 and 2, the gage may comprise a pair of members 1 and 2 which are mounted for relative motion transversely to the axis of the work to be gaged, and, as shown, this motion is rectilinear. For this purpose the member 2 is provided with portions engaging in parallel ways, one of which is shown at 3 in the member 1, the member 2 thus being mounted for rectilinear movement on the member 1.

A dial indicator 4 is carried by the supporting or fixed member 1 and its actuating stem 5 bears against an ex- 2,762,131 Flatented Sept. 11, 1956 tension 6 from the movable member 2. A spring 7 engaging this extension 6 and reacting between it and a portion of the member 1 presses this extension 6 against the stem 5 of the indicator and tends to separate stud portions 9 and 10 of a pair of gaging anvils 11 and 12 which are secured to the members 2 and 1, respectively. A finger lever 14 may be actuated to retract the movable member against the spring 7 and open the gage. These stud portions have externally threaded arcuate portions 15 and 16 which are pressed into engagement with the threads of the work piece when the gage is closed thereon. These arcuate portions 15 and 16 are each of a radius equal to or slightly less than that of the corresponding portions of the threads of a standard work piece and when a standard work piece is in gaging position, these arcuate portions 15 and 16 properly engage the threads of this work piece as shown in Figure 5, and the dial indicator is then adjusted for Zero. The indication of the dial indicator when a work piece to be tested is being gaged will then give an indication of whether or not the work piece is of the proper size.

Adjacent to one edge of each of the arcuate portions 15 and 16 are second arcuate portions 17 and 18, these second arcuate portions being on the two anvils in the same direction angularly, that is, as shown in Figure 3, the portion 17 is in clockwise relation to the gaging portion 15'- and similarly the arcuate portion 18. is in clockwise angular relation to the gaging face 16. These arcuate portions 17 and 18,, however, are arcs of smaller radius than those for the gaging surfaces 15 and 16., For example, the maximum radius for the gaging arcuate por tions 15 and 16 is shown at R in Figure 3, the center of curvature being in a diameter dd which passes through both of these arcs and which lies in the direction of relative motion of the anvils when they are moved between open and closed positions. The radii of the arcuate portions 17 and iiare equal and are somewhat less than the radius of the internal thread crests of a standard work piece, and they are struck from centers which when the anvils are in gaging position, as shown in Figure 3, are at 0, both of these centers lying substantially in the same diameter dd along which the anvils are moved rela-. tively in changing from gaging to open position. When the anvils are moved to open position these centers 0 move toward each other along the diameter dd until when they coincide, as shown in Figure 4, they are at the central axis of the standard work piece. The arcs 17 and 18 then form portions of the circumference ofacircle of slightly less diameter than the internal crests of the standard work piece, providing a clearance, thereb'etween later ally of the thread crests'as is clearly shown in. Figures 4. and 6. These arcuate portions 17 and 18are mainly smooth, although at their junctures with the arcuate portions 15 and 16, the threads of thelatter portions intersect. Each of the anvils, therefore, has an essentially unthreaded' convex guide portion, the curvature of which is described about an axis substantailly parallel to the axis of. curvla; ture of the threaded portion and at one end' intersects it so that it lies in the same plane transverse tothe axesj arcuate portions 15 and 16 do intersect the adjacent ends of the arcuate portions 17 and 18 and might therefore be engaged by the threads of the work piece and prevent free sliding motion, it is preferable to move the gaging anvils relatively in opening direction somewhat beyond the position shown in Figure 4- so that the end portions 20 and 21 of the arcuate portions 17 and 18" are spaced slightly wider than the portions 22 which contain threadgrooves but not greater than the internal diameter of the thread crests of the work piece, and become the guiding portions engaged by the Work piece, these portions 20 and 21 being removed from the threaded portions. This action avoids any necessity for relieving the surfaces of the arcuate portions 17 and 18 at 22 which are interrupted by thread grooves of the gaging portions 15 and 16. The remote ends of the arcuate portions 1517, and 16-18 are connected by chords 23 and 24 which are substantially parallel and may be at any desired angle between and 90 to the diameter d-d and they are sufiiciently spaced to permit the desired opening motion of the anvils, the portions 15-17 and 1618 each being somewhat less than a semi-circumference. An angle of approximately 45 for these chords 23 and 24 will usually be found quite satisfactory.

It will be noted that the gaging portions 15 and 16 are interrupted by recesses 25 forming acute angles 26 at their ends with the adjacent gaging surface. It is difiicult to remove chips and dirt from internal threads, as such threads are not readily accessible to cleaning elements, and should gaging of such threads while containing dirt and chips be attempted, the gage reading might be very unreliable. By the employment of the recesses 25 with the edges 26, it becomes an easy matter by relatively rocking the gage and work piece about the axis of the work piece to cause the edges 26 to cut through and scrape away the dirt and chips to properly engage the work, the dirt and chips entering into the recesses or traps 25. The recesses 25 are preferably arranged in the diameter along which the anvils are relatively moved when the gage is being opened or closed so as to be close to the portion of the thread gage most eifective in gaging.

In Figures 7 to 12 the arrangement of the anvils is shown for external gaging. Referring to these figures, a relatively stationary member 50 carries slidable thereon the movable member 51 which has an extension 6 bearing upon the stem of the dial indicator 4, this dial indicator being carried by the stationary member 50. External gaging anvils 52 and 53 are carried by the fixed and movable members 50 and 51, respectively. Each of these anvils has an arcuate portion 54 which is internally threaded to mate the threads of a standard plug, and these internally threaded gaging portions are in position to approach and recede from each other as the movable anvil is moved between gaging and open positions along the diameter d-d Each of these anvils is alsoprovided with a second arcuatetportion 55. This portion is described about a center c lying substantially in the diameter dd and of a radius slightly greater than the maximum radius of a standard threaded plug which is the maximum diameter of the thread crests.

When the anvils are moved to the open position shown in Figures and 12 so as to retract the arcuate'portions 54 from the gaging relation to the threaded plug shown in Figures 9 and 11, these centers 0 come together so that the arcuate portions 55 'are concentric with and spaced slightly outwardly of a work piece so that these arcuate portions 55 serve as portions of a smooth walled opening having sliding clearance between it and the work piece thread crests laterally of these crests and act as guides facilitating the placing and removal of the work piece. These arcuate portions 55 are unthreaded but where they approach the gaging arcuate faces 54, they are intersected by the threads thereof. Here, also, in order to avoid any chance of these intersecting portions interfering with the smooth guiding action, and also to avoid any necessity of relieving the gaging anvils at these points, preferably the opening action is allowed to proceed somewhat beyond the position shown in Figures 10 and 12 where the centers 0 coincide, whereupon the extremities 550 of the arcuate portions 55 remote from the gaging arcuate portions 54 are brought further toward the surface of the work piece and produce the guiding acti while the portions more remote therefrom. and

' ciently less than a semi-circumference to allow the necessary motion of the anvils to fully closed position.

Figures 13 and 14 show an external gage similar to that of Figures 7 to 12, inclusive, except that the external gaging faces 54 are provided with dirt recesses or traps 56 and scraping edges 57. Since it is a relatively easy matter to clean external threads, however, the presence of the dirt traps and scraping edges is not so important for external thread gaging as in the case of internal thread gaging, and it has the disadvantage of making the gage somewhat less convenient to test for accuracy due to the absence of gaging surfaces in the diametrical line dd of approach of the anvils.

While, as shown, the relative opening and closing motions of the anvils is rectilinear, this motion may depart somewhat from this. For instance, it may be arcuate, without requiring any changes over the construction shown, ordinarily such arcuate motion being on such a relatively long radius that it departs little from rectilinear motion.

From the foregoing description it will be seen that this invention provides for threaded gaging portions on the anvils and for unthreaded guiding portions facilitating the placing or removal of the work, but which do not interfere in any way with the gaging action of the threaded g'agingportionsQ It will also be evident that it is not essential that each gaging portion or each guiding portion be continuous along an arc so long as a sufficient area be provided to gage or to facilitate the guiding action.

This application is a continuation-in-part of my application for Screw Thread Gage, filed April 6, 1950,

Serial No. 154,331, now Patent 2,678,503, granted May 18, 1954.

From the foregoing description of certain embodiments of this invention it will 'be evident to those skilled in the art that various further changes and modifications may be made without departing from its spirit or scope.

I claim:

1. A thread gage for internal threads comprising a pair of gaging anvils dimensioned to fit within opposite halves of the threaded bore of a work piece to be gaged, each of said anvils having a gaging portion convexly curved and externally threaded for gaging said threaded bore, and a'guiding portion, spaced from'said gaging portion, presenting a smooth surface longitudinally of theaxis of said threaded bore, and means formounting said anvils with their said gaging and guiding portions respectively diametrically opposite one andother for relative opposite substantially rectilinear movement between a gaging position in which said gaging portions engage diametrically opposite portions of the thread of said threaded bore to gage the same and said guiding portions are spaced from said threadand a guiding position in which said gaging portions are spaced from said thread and said guiding portions are in slidable engagement with diametrically opposite portions of said thread for slidably guiding the work-on and off the gage.

2. A thread gage as defined in claim l'wherein each of said guiding portions is part of a 'convexly curved smoothsurface of its respective anvil, the radius of curvature of said surface being smaller than that of said threaded bore. i

- 3. A'thread gage as defined inclaim 1 wherein each of'said guiding portions is part of'a convexly curved smooth surface of its respective anvil and wherein the centers of curvature of said surfaces pass through a position of substantial coincidence in moving said anvils between gagingsand guiding positions;

4. A thread gage as defined in claim 1 wherein each of the gaging portions has a dirt-receiving recess extending transversely through the threads thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,337,018 Lockey et a1 Apr. 13, 1920 1,533,369 Blood Apr. 14, 1925 1,625,462 Frauenthal Apr. 19, 1927 

